Field of the Invention

The present invention relates to an oral care composition for minimizing staining of teeth.

Background of the Invention

Long-lasting whitening of teeth is of considerable interest to consumers. Foods and drinks such as tea, coffee and wine may form dental stains by directly depositing chromogens on the tooth surface. Attraction of materials to the tooth surface plays a critical role in the deposition of extrinsic dental stain. The chromogens in these beverages that are responsible for causing dental stain are known as tannins and are composed of polyphenols such as catechins. These materials generate color due to the presence of conjugated double bonds and are thought to interact with the tooth surface via an ion exchange mechanism.

Traditional tooth whitening methods involve either peroxide bleaching from kit formats or abrasive stain removal from toothpaste formats. These particles are essentially insoluble particles that remove extrinsic stain from the surface of the tooth via abrasion when applied with a brush. The present invention relates to a novel oral care composition that delivers effective levels of stain protection and prolongs the effects of tooth whitening by preventing staining of teeth. The invention discusses a stain repellent coating having a synergistic blend of a co-polymer and a Ca2+ chelating agent (phosphate salts). This helps to provide a protective stain coating on the tooth surface during the consumption of food/drinks post whitening treatments.

The copolymer for use in the present invention is a copolymer of polyester and polyol. Such a polymer is commercially sold as Texcare (from Clariant). Details of such a polymer has been published as US2015166938. This publication discloses this polymer for use as a soil release polymer in laundry detergent compositions and in fabric care products. There is no mention of such a polymer for use in oral care compositions. EP3031893 discloses (in Example 2) that Texcare polymers could be used as soil release polymers in laundry detergent compositions at 0.1 to 2wt%. Although this patent publication discloses oral care compositions, there is no mention of these types of polymers for use in oral care compositions.

It is thus an object of the present invention to provide for a composition for minimizing staining of teeth.

Summary of the Invention

An oral care composition comprising: (a) A polymer having the structure

R ¹ and R ² independently of one another are C1-4 (OCaHUjx (OCsHejy, the (OC2H4) groups and the (OC3H6) groups are arranged block-wise

x= 40-50, y= 1-7, a= 4-9; and

(b) an orally acceptable base selected from one or more of an abrasive, a surfactant, volatile alcohol or a humectant

Another aspect of the present invention relates to a method of minimizing or preventing the staining of teeth comprising the steps of:

(i) applying the composition of the invention on to a tooth surface for at least one minute; and

(ii) rinsing said surface to be substantially free of the composition.

Detailed Description of the Invention

Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use may optionally be understood as modified by the word“about”. All amounts are by weight of the final composition, unless otherwise specified.

It should be noted that in specifying any ranges of values, any particular upper value can be associated with any particular lower value.

For the avoidance of doubt, the word“comprising” is intended to mean“including” but not necessarily“consisting of’ or“composed of”. In other words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other irrespective of the fact that claims may be found without multiple dependency or redundancy.

Where a feature is disclosed with respect to a particular aspect of the invention (for example a composition of the invention), such disclosure is also to be considered to apply to any other aspect of the invention (for example a method of the invention) mutatis mutandis.

“Oral care composition” for the purposes of the present invention means a paste, powder, liquid, gum, serum or other preparation for cleaning the teeth or other surfaces in the oral cavity.

“Tooth paste” for the purpose of the present invention means a paste or gel dentifrice for use with a toothbrush. Especially preferred are tooth pastes suitable for cleaning teeth by brushing for about one minutes, preferably two minutes.

“Mouth wash” for the purpose of the present invention means liquid dentifrice for use in rinsing the mouth. Especially preferred are mouth washes suitable for rinsing the mouth by swishing and/or gargling for about half a minute before expectorating.

The present invention relates to an oral care composition comprising a polymer having the structure of compound of formula 1

Where the various R groups and the variables may have the following structures/ values:

R ¹ and R ² independently of one another are C1-4 (OC ₂ H ₄ ) _x (OC ₃ H ₆ ) _y , the (OC2H4) groups and the (OC3H6) groups are arranged block-wise;

x may have a value from 40 to 50, y may have a value from 1 to 7 and a may have a value from 4 to 9.

The molecular weight of the polymer is preferably from 500 to 20,000 Da, more preferably in the range of 5,000 to 20,000 Da. By molecular weight of the polymer, as per this invention is meant the weight average molecular weight of the polymer. The polymer is included in the oral care composition of the invention from about 0.1 to 5%, more preferably from 0.5% to 2.5% by weight of the composition.

The preferred polymers as per the above structures for use in the present invention are sold by Clariant under the tradenames Texcare SRN 170 and Texcare SRN 100. The structures of the above polymers are given below:

The composition of the invention preferably includes a phosphate compound. Phosphate compounds which may be included in the composition are one of more of

hexametaphosphate, di sodium hydrogen phosphate, sodium di hydrogen phosphate or tri sodium phosphate. Of these phosphate compounds the preferred compounds are hexametaphosphate or phosphates with more than six phosphorus atoms in the molecule, most preferably hexametaphosphate.

The structure of the various phosphate compounds referred to above are given below: Disodium Hydrogen Phosphate

Sodium Dihydrogen Phosphate

O

HO-P-ONa

OH

Sodium hexametaphosphate has the structure as give below:

The phosphate compound is preferably included in 0.1 to 5%, more preferably 0.1 to 3% by weight of the composition. The weight ratio of the polymer to the phosphate compound is preferably in the range of 1 : 1 to 5: 1 , more preferably in the range of 2: 1 to 4:1.

Without wishing to be bound by theory, the present inventors believe that phosphate compound e.g. hexametaphosphate, binds with calcium on the hydroxyapatite (HAP) surface thereby neutralizing the binding sites (Ca ²⁺⁾ that are responsible for the stain anchoring onto the HAP surface. The polymer on the other hand adsorbs on the surface of the HAP and reduces the surface energy by way of the hydrophobic segments of the polymer sitting on the HAP surface while the hydrophilic segments (PEG) protrude out like a brush repelling any stain (e..g. polyphenol molecules) that approach the HAP surface. The two actives viz. the phosphate compound and the polymer when used in combination complement each other and thus provide enhanced stain prevention.

The composition of the invention comprises an orally acceptable base. The orally acceptable base preferably comprises an abrasive, a humectant, a surfactant, a volatile alcohol or combinations thereof. More preferred orally acceptable bases include an abrasive, a humectant or mixtures thereof. The orally acceptable base preferably is included in as much as 99.8%, more preferably at as much as 96% by weight of the composition. The orally acceptable base is included in at least 80% more preferably at least 90%, by weight of the composition.

The oral care composition of the present invention may be delivered in the form of an ointment, a gel, a dentifrice or a mouthwash. Dentifrices include forms like toothpaste and toothpowder. A composition is most preferably presented in the form of a toothpaste, a toothpowder or a mouthwash.

Oral care composition of the present invention preferably comprises an abrasive. Gels usually contain silica, whereas opaque creams generally contain calcium based abrasives, especially chalk. It is preferred that the composition of the invention comprises silica as the abrasive. Such a composition comprising abrasive silica is generally in the form of a gel. Abrasive silica for incorporation in the composition of the invention is preferably one with a low refractive index. It may be used as the sole abrasive silica, or in conjunction with a low level of other abrasive silicas, e . g . those according to EP236070. The low refractive index silicas , used as abrasives in the present invention are preferably silicas with an apparent refractive index (Rl) in the range of 1.41 to 1.47, preferably 1.435 to 1.445 , preferably having a weight mean particle size of between 5 and 15 m , a BET (nitrogen) surface area of between 10 and 100 m ² /g and an oil absorption of about 70 - 150 cm ³ /100 g, but abrasive silicas with a lower apparent refractive index may also be used . Typical examples of suitable low refractive index abrasive silicas (e.g. having an Rl of between 1.435 and 1.445) are Tixosil 63 and 73 ex Rhone Poulenc ; Sident 10 ex Degussa; Zeodent 113 ex Zeofinn; Zeodent 124 ex Huber, Sorbosil AC 77 ex Crosfield Chemicals (having an Rl of approximately 1.440). The amount of these silicas in the composition of the present invention generally ranges from 5-60% by weight , usually 5-20% by weight of the composition.

In a preferred embodiment, the composition comprises a thickener. Thickeners that may be used in this invention include, sodium carboxymethyl cellulose (SCMC), hydroxyl ethyl cellulose, methyl cellulose, ethyl cellulose, gum tragacanth, gum arabic, gum karaya, xanthan gum, sodium alginate, carrageenan gum, guar gum, Irish moss, starch, modified starch, silica based thickeners including silica aerogels, magnesium aluminum silicate (e.g., Veegum), Carbomers (cross-linked acrylates) and mixtures thereof.

Typically, thickening silica, sodium carboxymethyl cellulose and/or a Carbomer is/are preferred thickeners for use in the composition of the invention. When a Carbomer is employed, those having a weight-average molecular weight of at least 700,000 are desired, and preferably, those having a molecular weight of at least 1 ,200,000, and most preferably, those having a molecular weight of at least about 2,500,000 are desired. Mixtures of Carbomers may also be used herein.

In an especially preferred embodiment, the Carbomer is Synthalen PNC, Synthalen KP or a mixture thereof. It has been described as a high molecular weight and cross- linked polyacrylic acid and identified via CAS number 9063-87-0. These types of materials are available commercially from suppliers like Sigma.

In another especially preferred embodiment, the sodium carboxymethyl cellulose (SCMC) used is SCMC 9H. It has been described as a sodium salt of a cellulose derivative with carboxymethyl groups bound to hydroxy groups of glucopyranose backbone monomers and identified via CAS number 9004-32-4. The same is available from suppliers like Alfa Chem.

Thickening silica is especially preferred to be used in gel toothpastes. Gel toothpastes generally contain upto 8.5 wt% thickening silica whereas opaque toothpastes typically contain 3 to 4 wt% thickening silica.

When present, preferred thickening silicas include AEROSIL T series from Degussa or the CAB-O-SIL series from Cabot Corporation, silica gels such as the SYLODENT or SYLOX series from W. R. Grace & Co or precipitated silica such as ZEOTHIX 265 from J. M. Huber Corporation. Useful silica thickeners also include ZEODENT 165, ZEODENT 163 and/or 167 and ZEOFREE 153, 177, and/or 265 silicas, all available from J. M. Huber Corporation. Other preferred thickening silicas include MFIL, MFIL-P (From Madhu Silica, India), SIDENT 22 S and AEROSIL 200 (Ex. Evonik Industries), SYLODENTand PERKASIL thickening silicas from WR Grace & Company and Tixosil 43 and 331 from Rhodia, synthetic finely divided pyrogenic silica such as those sold under the trademarks SYLOID 244, SYLOID 266 and AEROSIL D- 200.

Thickener, when present, preferably makes up from 0.01 to about 10%, more preferably from 0.1 to 9%, and most preferably, from 1.5 to 8% by weight of the composition.

Suitable humectants are preferably used in the oral care composition of the present invention and they include, for example, glycerin, sorbitol, propylene glycol, dipropylene glycol, diglycerol, triacetin, mineral oil, polyethylene glycol (preferably, PEG-400), alkane diols like butane diol and hexanediol, ethanol, pentylene glycol, or a mixture thereof. Glycerin, polyethylene glycol, sorbitol or mixtures thereof, are the preferred humectants, most preferred ones being glycerol (also known as glycerine) and sorbitol.

The humectant may be present in the range of from 10 to 90% by weight of oral care compositions. More preferably, the humectant makes up from 25 to 80%, and most preferably, from 45 to 70% by weight of the composition, based on total weight of the composition and including all ranges subsumed therein. Preferably, an oral care composition comprises a surfactant. Preferably the

composition comprises at least 0.01% surfactant by weight of the composition, more preferably at least 0.1% and most preferably from 0.5 to 7%. Suitable surfactants include anionic surfactants, such as the sodium, magnesium, ammonium or ethanolamine salts of C8 to C18 alkyl sulphates (for example sodium lauryl sulphate), C8 to C18 alkyl sulphosuccinates (for example dioctyl sodium sulphosuccinate), C8 to C18 alkyl sulphoacetates (such as sodium lauryl sulphoacetate), C8 to C18 alkyl sarcosinates (such as sodium lauryl sarcosinate), C8 to C18 alkyl phosphates (which can optionally comprise up to 10 ethylene oxide and/or propylene oxide units) and sulphated monoglycerides. More preferably the surfactant comprises or is an anionic surfactant. The preferred anionic surfactants are sodium lauryl sulphate and/or sodium dodecylbenzene sulfonate. Most preferably the surfactant is sodium lauryl sulphate. Other suitable surfactants include nonionic surfactants, such as optionally

polyethoxylated fatty acid sorbitan esters, ethoxylated fatty acids, esters of

polyethylene glycol, ethoxylates of fatty acid monoglycerides and diglycerides, and ethylene oxide/propylene oxide block polymers. Other suitable surfactants include amphoteric surfactants, such as betaines or sulphobetaines. Mixtures of any of the above described materials may also be used. Most preferred surfactants are an alkali metal alkyl sulphate or a betaine.

Water may preferably be included in 5 to 95%, in particular 10 to 75%, and especially at from 10 to 60%, further more preferably 10 to 45% by total weight of the

composition.

When the oral care composition of this invention is a toothpaste or gel, the same typically has a viscosity from about 30,000 to 180,000 centipoise, and preferably, from 60,000 to 170,000 centipoise, and most preferably, from 65,000 to 165,000 centipoise.

The oral care composition of the present invention may contain a variety of other ingredients which are common in the art to enhance physical properties and performance. These ingredients include antimicrobial, anti-caries agents, plaque buffers, fluoride sources, vitamins, plant extracts, desensitizing agents, anti-calculus agents, biomolecules, flavors, proteinaceous materials, preservatives, opacifying agents, coloring agents, pH-adjusting agents, sweetening agents, particulate abrasive materials, polymeric compounds, buffers and salts to buffer the pH and ionic strength of the compositions, and mixtures thereof. Such ingredients typically and collectively make-up less than 20% by weight of the composition, and preferably, from 0.0 to 15% by weight, and most preferably, from 0.01 to 12% by weight of the composition, including all ranges subsumed therein.

According to another aspect of the present invention there is provided a method of minimizing or preventing the staining of teeth comprising the steps of (i) applying the composition of the present invention on to a tooth surface for at least one minute; and (ii) rinsing the surface to be substantially free of the composition. The method is preferably non-therapeutic i.e for achieving cosmetic benefits.

The invention will now be illustrated with the help of the following non-limiting example.

Examples

Examples 1-4: Effect of inclusion of the polymer as per the invention and additionally effect of inclusion of phosphate compound on anti-stain benefit: Pellicle coated HAP discs were treated with the dentifrice (with base composition as given in Table - 1 below) containing various stain repellent ingredients as listed in Table - 2. The procedure used to simulate staining of teeth and the whiteness of the disks was measured as detailed below: HAP disks were soaked in 2 ml saliva/water and placed in the oven at 37°C for 30 minutes. The disks were rinsed with milli Q water and dabbed to remove excess water. Pellicle coating HAP disks (moist) coated were soaked with 2 ml of tooth paste slurry or model base for 5 minutes. Disks were brushed for 1 minute and rinsed with 100 ml Milli Q water. Initial L*, a*, b* values were monitored using a spectrophotometer.

Treated HAP disks were soaked in 2 % tea solution (2 grams black tea in 98 ml boiling water and stirred for 5 minutes) at 37°C for 10 minutes. Staining cycle was repeated for 3 times and the stained HAP disks were brushed/ rinsed after each staining cycle. The L*, a*, b* values were monitored after each staining cycle. Delta E value was then calculated using the following equation. DE =V((L * initial - L * final) ² + (a * initial - a * final) ² + (b * initial - b * final) ² )

Table - 1

The DE values of HAP disks treated with the various compositions is given in the table

-2 below:

Table - 2

In the table above, Texcare SRN 170 is sourced from Clariant and HMP refers to sodium hexametaphosphate sourced from Sigma.

The data in the table -2 above indicates that oral care composition as per the invention (Example 2) provides superior anti-staining efficacy (as evident by the low DE values). Use of phosphate compound (Examples 3 - 4) provides for further improvement in anti-staining efficacy.